Tire pressure indicator switch



Sept. 17, 1940. H l HULL 2,215,153

TIRE PRESSURE INDICATOR SWITCH Filed NOV. 1, 1938 Jcfoafam Zf.

i @M l I mrow/m Patented Sept. 17, 1940 UNITED STATES PATENT OFFICE 1 Claim.

This invention relates to certain new and useful improvements in tire pressure indicator switches.

The primary object of the invention is to provide a tire pressure indicator switch controlling the operation of a signal, preferably a lamp, to indicate when the air pressure in a motor vehicle tire exceeds or falls below a predetermined amount so that the operator of the vel0 hicle would be aware at all times of the air pressure conditions oi the tire.

With the above and other objects in view that will become apparent as the nature of the invention' is better understood, the same consists in the novel form, combination and arrangement of parts hereinafter more fully described, shown in the accompanying drawing and claimed.

InI the drawing:

Figure 1 is a fragmentary side elevational view of a motor vehicle wheel, the axle thereof being shown in section together with a part of the wiring arrangement and signal lamp indicating high and low tire pressures,

l5.2i; Figure 2 is an enlarged fragmentary sectional view showing the switch device mounted upon the wheel rim and exteriorly of the inner tube of the tire and in its open position,

Figure 3 is a detail sectional view, similar to Figure 2, showing the switch device in its extended position in contact with a terminal responsive to low tire pressure, and

Figure 4 is a perspective view of the switch device or arm.

' 35 Referring more in detail to the accompanying drawing, the reference character 5 designates a pneumatic tire shoe housing an inner tube 6 and mounted upon a wheel rim 1. the rim being anchored to the wall 8 of the wheel that includes a circular flange 8 extending over a stationary element of the wheel assembly such as a casing or brake drum I0. The wheel is illustrated in Figure 1 as being mounted on an axle II.

An electric terminal comprising a stem I2 has the lower end thereof threaded as at I8 for passage through an opening Il in the Wheel rim 1, the stem I2 carrying a conically shaped flange I5 intermediate its end that rests in a pocket I8 at the outer side of the opening I4 within the tire shoe, the threaded end I3 of the terminal stem I2 being locked in the rim 1 by the nut I1. A disk head I8 is carried by the end of the stem I2 within the tire, the disk head I8 and conical flange I5 constituting electrical terminals.

A switch arm I9 shown in detail in Figure 4 as having an offset end 20 provided with apertures 2| is mounted upon the inner face of the wheel rim 1 by means of anchor screws 22 so that the switch arm I9 is spaced from the wheel 5 rim 1 to provides pocket 23 in which the contact terminals I5 and I8 are disposed, the switch arm I9 being engaged with the outer face of the inner wall of the inner tube 8 for holding the same in an inwardly arched position as l0 shown at 6l. The free end of the switch arm I8 is bent upon itself as at 24 with the returnbent portion slotted to provide a fork 25 straddling the stem I2 of the terminal and normally positioned between the contact members I5 and l5 I8. The normal position of the fork25 midway of the contact members I5 and I8 and the tensioning of the resilient switch arm I9 is accomplished by the adjusting screw 28 threaded through the rim 1 and engaged with said 20 switch arm, adjustment of the screw 28 determining air pressure within the tires.

An electric conductor 21 has one end attached to the threaded end I3 of the terminal stem I2 while the other end of the conductor 21 carries 25 a carbon brush contact 28 mounted in a guide 29 carried by the flange 8, the carbon contact 28 being in wiping engagement with the brake drum I0. A conductor wire 30 extends from `the brake drum I0 to the source of electrical 30 Aenergy 3| and from said source 3|, a wire 32 extends to a signal lamp 38 on the instrument board 34 of the motor vehicle, the other wire 35 from said lamp 33 being ground as at 38 while the mounting of the swltcharm I 9 upon a5 the wheel rim 1 forms the other ground for the circuit.

When the pneumatic tire has been inflated to the desired pressure, the fork 25 of the switch arm I9 is positioned midway the contact elements I5 and I8 of the terminal I2, but should pressure in the tire fall below a predetermined amount, the arched portions 8 of the inner tube 6 will stretch and flex to permit the fork 25 of the switch arm I9 to move into engagement with the contact element I8 for closing the circuit through the storage battery or source of energy to the signal lamp 33 and ground. In a similar manner, should the pneumatic develop excessive conditions due to heat or other causes, 50

the arched portion 6a of the inner tube would bear with greater force on the switch arm I8 and move the fork 25 of the switch arm into engagement with the contact element I5 and thereby close the circuit to the signal lamp. 55

From the above detailed description of the invention, it is believed that the construction and operation thereof wiii at once be apparent, and while there is herein shown and described the preferred embodiment oi the invention, it is nevinterposed between the terminals, said terminals comprising a stem anchored in the rim with the terminals disposed between the rim and inner tube, said switch arm having one end anchored to the rim and the other end offset from the rim and engaged with the inner tube to provide a pocket between the inner tube and rim for the mounting of the terminal, and a screw device threaded through the rim and engageabie with t the switch arm adjacent the anchored end thereof for setting the normal position of the switch blade relative to the terminals.

HOWARD L. HULL. 

